Pneumatic safety control for presses



Jan. .6, 1942.v s. T. WILLIAMS 2,268,733

l v PNEUMATIC SAFETY coNTEoEFR PREssEs Filed Nov. 50, 1938 2Sheets-Sheet l ngz.

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Jain. 6, 1942. s`. T. WILLIAMS -PNEUVMATVIO SAFETY CONTROL vFOR PRESSES2 Sheets-SheetI 2 Filed Nov. Aso', 1958 llllI-ll I y INVENTOR l `7 l ,l

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Patented Jan. s, 1942 PNEUMATIC SAFETY COTROL FOR PRESSES semen T.Wmiams, euerose, N. Y., assigner to Scovill Manufacturing Qompany,Waterbury, Conn., a corporation of Connecticut Application November'30,1938, Seal No. 243,220

4 claims. (ci. 121-38) My lpresent invention relaftes to safety controldevices for power presses and the like, and more Y particularly to such'safety devices which are pneumatically controlled.

The prevention of injury to press operators of power presses has longreceived the attention of safety engineers and labor boards and much hasbeen done to reduce the hazards topersonal injury incident to pressoperations. Various forms of safety appliances in thetnature of safetyclutches, electrical devices and mechanical shields have been devised,and while these have Fig. dis a fractional view\of a'modied form ofcut-out valve.

Fig. 5 is a longitudinal section of a further detail of my'invention,certain parts thereof being shown in elevation. Although my invention iscapable of use with any type of press or machine which has a movablehead adapted to move toward and away from a complemental member andbetween which members the hands of an operator mustbe positioned'in thehandling of the work to be operated met with varying degrees of successand recogi nition. on the whole they have been open vto one objection oranother. Among the primary ob,- jections met with by these safetydevices are: (1) their tendency to slow down the press operation; I2)their high installation cost; (3) their non-foolproof character; and (4)theirsafety characteristics could be circumvented by an operator whodesired to speed up production.v

My present invention provides a4 safety device -for power presses andtheV like Awhich overcomes the various objections and limitationsabovementioned. In its underlying concept my invention relies uponcompressed air to operate a plungerfor tripping a clutch on the driveshaft of the press or for operating an equivalent means, and a pluralityof control valves so disposed with relation to the operating head of thepress that both hands of an operatormust be used to operate said valvesandl be well away from danger when doing so; and further, said valvesare shielded so that they can not be accidentally operated. My inventionis capable of installation on machines that are equipped with eithernonrepeat or repeating type clutches and in every case the safety deviceembodies at least twomanually operable valves and one or more cut-outvalves of novel design.

The principle, construction and operation of my improved pneumaticcontrol safety Idevice will'be betterl understood from the deaileddescription which follows, when considered in connection with theaccompanying drawings which show a practical embodiment of my invention,Vand wherein: A

g Figure l is a perspective View ofP a power press showing myinventionapplied'thereto.

upon which is mounted a clutch (not shown) of as pivotally mounted atI8r to the press frame.

upon by the machine, I have shown my safety device applied to av powerpress A of conven v tional design having a movable head I0 which-carriesa die Il for 4cooperation with a complelmental die I2 mounted onthe base ofthe press.

The head I0 is reciprocable s o as to bring the dies'li and I2 intooperative position to the work being acted upon, and reciprocation ofthe head I0 isprovided by rotation of the shaft I3 any approved type.'As herein'shown, the clutch is adapted to be tripped by a clutch trip I4carried by a rod I5, one end of which carries a piston I6 mounted in acylinder I'I which-isshown For operating the clutch trip only when thehands of the operator are well away from danger,

I have provided a pair of manually4 operable sure operated valve C whichform valves B and B2 and a cut-out or automatic prespart of a pneumaticcircuit adapted to establish fluid communication between the interior ofthe cylinder Il with a source of compressed air. In Fig. 1 of thedrawingsv I have shown included in the pneumatic circuit, a cut-outvalve C, a second cutloutv valve D, and a relief valve E. The structuresand functions for the valves B,.B.2, C, D and E, will be presentlydescribed.

^ The manually operable valves B and B2i are identical in constructionand each consists of a l hollow casing I9 hav/ing lateral tubular o'setsor projections 20 and 2| providing induct and educt openings,respectively, in thecasing. With- Fig. 2 is a longitudinal sectionthrough one of in the casing between the lateral offsets is a shoulderupon which is mounted a valve packing seat 22 which is held in placevbye. tubular plug 23 having lateral openings y24 therein, the said`plug'being screw-threadedly or otherwise held in position within thecasing. Mounted within the casing for engagement with the packing seat22 A is a valve check member 25l the lower portion of whichl ishollowedout and encloses a helical spring 26 for normally holding the valveagainst its seat. The valve check 25 above the seating portion thereofis formed with an axial pin 21, the upper end 28 of which is of tubularform and of a diameter to snugly slide through the axial opening in thetubular plug 23, and said tubular portion of the pin, at its lower end,-s formed with lateral openings 29. To insure against leakage and toprovide an air seal between the top of the tubular plug 23 and the topof the hollow portion 28 of the valve pin 21, I connect said partstogether by a coneshaped packing 39. Anysuitable means may be employedfor holding this packing in contact with said parts, .and as hereinshown, the packing which is formed as a separate part has a sliding twith the hollow portion of the valve check pin and is held in clampingengagement with the tubular plug 23 by a tubular member 3| whichscrew-threadedly engages Within the casing I9. Mounted for telescopicmovement within the tubular member 3i is a plunger 32, the inner end ofwhich is recessed as at 33 to engage over and seal the open end of thehollow portion of the valve check pin when the plunger is depressed inthe act of unseating the valve check 25. The

plunger 32 is of a length to extend beyond the u top of the tubularmember 3| and is normally urged outwardly by a helical spring 35 mountedbetween a shoulder within the tubular member 3| and a shoulder on theplunger 32. For limiting the extent of the plunger movement and forholding itagainst separation from the tubular member 3|, the plunger isformed with a slot 36 through which extends a -pin 31 carried by thetubular member. For facilitating movement of the plunger by the hand ofan operator, the plunger at its outer end is provided with an enlargedmushroom head 34. The tubular lateral oisets 2|) and 2| are eachthreaded for connection with screw-threaded nipples 3B to which areattached sections of hose or flexible conduits 39, 39', 392, and 393forming a part of the pneumatic circuit. The tubular member 3| is alsoformed with a lateral opening or vent 49 which, it will be observed,provides open communication through the tubular portion 28 of the valvecheck pin and thelateral openings 24 in the tubular plug 23, with thebore through the lateral offset 2|, the educt opening of the valve B,when the,

check valve 25 is seated. When the valve check 25 is unseated it will beappreciated that this open communication is cut off by the seal providedby the engagement of the lower end of the plunger 3 2 with the conedpacking 30.

The automatic pressure operated cut-out valve C consists of a casingformed of a central substantially cylindrical tubular element 4|, theends of which are screw-threadedly connected to tubular end members 42and 43y each of which terminates in an outwardly-directed nipple 44 towhich an'end of the conduit or hose 39 is suitably connected. Mountedwithin the casing provided by the elements 4 I, 42, and 43, is a tubularmember 45 having a bore substantially flush with the bore through thenipple. end of the element 42 and having an outwardly directed flange 46which is clamped against a flat surface in the element 42 by thescrew-threaded connection between said elements 4| and 42. Surroundingthe tubular element 43 in slightly spaced relation thereto is a tubularplunger check valve 41 which at its end adjacent the flange 46 is formedwith a flange 48 and carries a piston packing 49 having a diameter toair-tightly move within the cylindrical bore of the element 4|.

bearing at one end against the flange 48 is a helical spring 50, theopposite end of which bears against an inwardly-directed flange 5| onthe tubular element 4| for the purpose of exerting a force upon theplunger valve for normally holding it in its unseated position as shownin Fig. 3. The plunger valve 41 at its other end is closed and formedwith an annular ring 52 rearwardly of which the plunger valve is formedwith lateral openings 53 leading from the interior of the tubularplunger to the duct through the cut-out valve. The closed end of theplunger valve is adapted to engage a valve seat packing 54 mountedwithin the tubular element 43 and held therein by a sleeve 55 which isclamped between the annular flange 5| and said packing in the assemblyof the elements 4| and 43, there being also provided a packing 56between the sleeve 55 and the flange 5|, which packing engages the outerwall of'the plunger valve 41 to provide an air-tight seal therewith. Thepacking 54 consists of two washers which are pressed over a tubularsleeve 51 having an outwardly-directed flange or rib 58 intermediate itsends. The element 43 between the nipple 44 thereon and the packing 54therein is formed with a chamber having a spider 59 for guiding the stemof a oating valve 60, the face thereof which engages the packing 54being of conical form and of smaller effective area than the oppositefacev of said valve. The function for this construction will presentlybe explained. To prevent tamper# -valve therein corresponding to theiloating valve 90.

The relief valve E may be of any approved form and its primary functionis to provide an adjustable vent for the venting of air from thecylinder l1.. As shown, it consists of a plug 6|. screw-threadedlymounted in a T-ltting 62 which in turn is connected at one end through anipple 63 to a sectiony of hose 39, and at its other end through ascrew-threaded nipple 54 to a head 55 mounted on the cylinder I1. Theplug 6l lhas a bore therethrough, and intermediate the ends thereof ithas a valve seat 56 upon which is adapted to seat a valve member 51having 'a passage 68 therein through which air may vent when the valveis unseated. For adjusting the valve plug 31 it is screw-threadedlymounted into the plug 9| and formed at its outer end with a ker! 69adapted to accommodate a screwdriver. A lock-nut 10 serves to lock thevalve in adjusted position. Enclosing the outer end of the plug 6| is adust cap 1| having a vent opening 12 therein.

Mounted in the cylinder head $5 is a gland packing 13 for insuringagainst air leakage from the cylinder around the plunger rod. The glandpacking is held in place by a plug 14 which also serves as abearing forone end of a compres- Surrounding the plunger check valve 41 and 7|conveniently attached to the machine by means .with a non-repeat or4single stroke clutch the cut-out valve D and the vent valve E can bedispensed with and adirect hose connection may be provided between theright hand-operating valve B2 and the cylinder I1. Alternatively, thesame end may be accomplished byl merely closing the vent in the valveE.' When the safety device is tobe usedwith a repeat type clutch thevent in the valve E is opened to Vallow for venting of the cylinder. 1Operation-With a safety device as illustrated and hereinbeforedescribed, when used with a non-repeat type clutch, the procedure andoperation are as follows:

I'he right hand operating valve B1 'must be pressed down slightly inadvance of the left hand operating ,valve B or simultaneously therewith.

, When this is done the compressed air from the sourcepasses through thepneumatic circuit into the cylinder I1 and forces the piston downwardly,which action trips the clutch and operates the press. Whenrthe operatingvalves B and B2 are opened in the-manner specied, apu or blast of airpassesl through the pneumatic circuit to act upon the piston, and afterso acting, the incoming air pressure operates to move the plunger valve41 of the'cut-out valve C against the seat 54,.and saidl valvewillremain seated so long as the left hand operating valve V is held open.

when the hand is removed'frbmthe left hand operating valve B the checkvalve therein will fseat under the force of the .spring 26, thecompressed air entrapped in the cut-out valve C will vent through theopening 40 in the valve B and permit the plunger valve 41 to unseat.When the hand is removed from the right hand operating valve B2, the airfrom the cylinder I1 will I ventthroughthe opening 40 in said valve.

As the air is released from the cylinder I1 the clutch trip I 4 isreturned to its operating position and the press can not again operateuntil the clutch is again tripped.

. I f either of the manually operable valves B or y B2 is tied dow'n orheld down, the cut-out valve C functions to prevent the piston in thecylinder from operating the clutch, because, as above described, if theleft hand valve B is held down, the plunger valve 41 will remain seatedand prevent the passage of air through the-pneumatic circuit to thecylinder, while if the right hand operating valve B2 is held down, thepress will operate once; and once only as the check valve 60 of cut-outvalve C holds the air in the piston and will not let it return.Furthermore as the effective area of the valve 60 acted-upon by thetrapped back pressure in cylinder I1 is greater than the effective areaof the seating face of said valve, it will be apparent that the Kincoming air through the cut-out valve C upon unseating of valve B willbe seat the valve 60. f

Where the safety device is used with a reinsufcient to unpeating typeclutch, the' action is substantiallyA the same as with the non-repeatclutch above described, except that the airvfrom the cylinder is ventedthrough the relief valve E, Aand this this connection if either of thevalves B or B2 are tied down or held down, the press would not againtrip because if the lleft hand valve B is held down the valve 52 of thecut-out valve C 5 will remain closed and prevent the admission of air tothe cylinder I1, while if the right hand valve B2 is held down, thevalve plunger 52a in the cut-out valve D Willbe held closed, since thecompressed air entrapped between the check Gli 10 in the cut-out valve Cand the valve 52a ofthe cut-out valve D will operate to hold said valve62a upon its seat. y

It will thus be seen thatJ the safety device surev responsive member anda pneumatic circuit having therein means adapted to permit the passageof onlya surge of compressed air from a source to said fluid' responsivemember, said last mentioned. means comprising at least three valves inseries, two of ywhich are manually unseatable and the third is a cut-outvalve, each of the manually unseatable valves lcomprising a casingvhaving therein a valve seat, a spring- -seated check valve, an inlet andan outlet on opposite sides of the valve seat and a vent opening,

means adapted to establish communication between the outlet and theatmosphere when the check valve is seated and shut off such communiwcationwhen the check valve is unseated, the

inlet of the first of said two manually unseatable valves beingconnected to the fluid supply and its outlet being connected to theinlet of the cutout valve, they second of the manually unseatable lavalves having its inlet connected to the outlet of the cut-out valve andits outlet connected to the v.Aiuid pressure responsive member, and thecutout valve comprising a casing having an inlet.

an outlet anda spring-loadedl normally unseated check valve therebetweenadapted to permit only a surge of compressed air to pass through thecasing and then seat to cut ofi said flow, such surge of compressed airthrough the pneumatic circuit from the source to the pressure responsive55. member being possible only when the manually unseatable valveconnected to the outlet of the cut-out valve is unseated in advance of,or simultaneously with, the other manually unseatable valve.

to claim 1, wherein the spring-loaded check valve of the cut-out valveafter closing will remain .closed so long as the first of the twomanually unseatable valves remains open.

3. Pneumatic safety control means according to claim 1 wherein the.cut-out valve also has a floating check valve therein, between thespringloadednormally unseated check valve and the I outlet, which isadapted to open under incoming ,10 air pressure and closev by the backpressure from the fluid pressure responsive member if the second of thetwo manually unseatable valves is held open after operation of thepress.. 4. Pneumatic safety control means for opera- N tion of a pressor the like comprising a fluid 2. Pneumatic safety control meansaccording pressure responsive member and a pneumatic cirpassage of onlya surge of compressed air from a source to reach said uid responsivemember, said means comprising ve valves in series, two of which aredisposed to be separately manually unseatable, two are automaticallyoperable cutout valves, and the ,fifth is a relief valve, each of themanually unseatable valves comprising a casing having therein a valveseat, a spring-seated check valve, an inlet and an outlet on oppositesides of the valve seat, and a vent opening, means adapted to establishcommunication between the outlet and the atmosphere when the check valveis seated, and shut oif such communication when the check valve isunseated, the inlet of the 4rst of said two manually unseatable valvesbeing connected to the fluid supply and its outlet being connected tothe inlet of the rst cut-out valve, the second of the manuallyunseatable valves having its inlet connected to the outlet of the firstcut-out valve and its outlet connected to the inlet of the secondcut-out valve, and the outlet of the second cut-out valve beingconnected to the uid pressure responsive member, each of said cut-outvalves comprising a casing having.

sure responsive member and adapted to vent the compressed air therefromafter operation of the press.

SELDEN T. WlLLIAMS.

